Various detection devices and detection cells have been designed for identifying and characterizing small molecules. Typical devices may include, UV VIS, fluorimeters or micro-fluidic devices. Most of these devices provide some type of detection cell with limited volume for holding the sample while light is passed through the cell. This allows for conservation of sample and increase of signal to noise (i.e. improve characterization and detection).
Most of these devices and cells operate by first placing a buffer or a fluid medium in the detection cell. Then light of a defined wavelength is passed through the medium and the properties recorded. Next, a sample is then typically dissolved in the same fluid medium and the combined mixture is placed in the detection for a reading. Various light wavelengths can then be passed through or scanned through the device. Light is then transmitted or reflected from the molecules in the solution and the results recorded.
More recently, micro-fluidic devices are being used in identifying and characterizing small molecules. These devices avoid the problem of having to use large amounts of sample, transfer sample and take multiple readings to remove baseline contamination readings or low signal to noise. Smaller and smaller samples have been detected, characterized and recaptured using these devices. In certain instances it is possible to quantity the molecules in solution based on some simple laws. For instance, many ultraviolet and visible absorption methods adhere to the Beer Lambert law. The Beer Lambert Law provides that:ε×bC=A  (1)where C is the concentration in moles per liter and is assumed to be constant,A is the minimum detectable absorbance, ε is the molar extinction coefficient and b is the path length (typically 1.0 cm). As one will note from this law that as the concentration C or the path length b are increase the absorbance also increases. In other words the minimum level of detection is increased.
With micro-fluidic devices there are additional parameters that must be considered. For instance, path length (L), the volume (V) as well as well as the cross-sectional area (CSA) of the detection cell are also important in effecting the sensitivity level.
Ideal conditions for improving the signal to noise ratio (sensitivity) require decreasing V, increasing L and decreasing CSA. This provides the optimal conditions for obtaining the best sensitivity. However, most detection cells or devices do not allow for improving each of these parameters. Typically the improvement of one condition causes a negative effect on the other parameters. In the end, this does not improve overall sensitivity levels. For this reason there is a need to improve the overall signal to noise ratios of detection devices and detection cells. In addition, it would be desirable to provide a detection device or cell that minimizes overall sample volume, yet increases L and decreases CSA. To date, few devices and/or detection cells provide the ability to improve each of these parameters to provide improved sensitivity. Most of the present detection devices and detection cells do not provide flexibility for improving these parameters. In addition, it is also desirable to provide a mode of sample transfer and preparation that avoids loss of sample and maximizes the overall sensitivity of the sample detection cell. These and other problems experience by the prior art have been obviated by the present invention.